Receiver for pulse position indicating systems



.Fy 9, 1946. R. s. HOLMES ET AL RECEIVER FOR PULSE POSITION INDICATINGSYSTEMS File'd Nov. 29', 1941 2 Sheets-Sheet' l Snoentor iiiiii l iiiiii2 sheets-*sheet 2- A A A A A l V V V W V V @www/wm@ v @Emy 711555 R. s.HOLMES ET AL Filed Nov. 29, 41941 July 9, 1946.

RECEIVER FOR PULSE POSITION INDICATING SYSTEMS 7a 6,6/0 of 705 l gy 70@m05 0F Maffe/ WMI? fw ma@ Patented July 9, 1946 RECEIVER FOR PULSEPOSITION INDICATING SYSTEMS Ralph S. Holmes, Haddoneld, and John P.

Smith, E rlton, N. J., assignors to Radio Corporation of America, acorporation of Delaware Application November 29, 1941, Serial No.420,928

(Cl. Z50-11) 12 Claims.

This invention relates to improvements in receivers for a pulse positionindicating system, and more particularly to a receiver and associatedcathode ray pulse timing tubes which are provided with means forblanking undesired portions of the timing traces.

In a copending application Serial No. 420,944, filed November` 29, 1941,by Irving W011i and Ralph S. Holmes, a system is described forindicating position by means of radio pulses. The

pulses are radiated in predetermined time relation from a plurality oftransmitters at known locations. The pulses are received at an unknownpoint. By observing the relative times of arrival of signals from threetransmitters, the location of the point of reception can be iixed withrespect to the pulse signal sources. In the described system cathode raytubes are used as decade timing indicators. The cathode ray beams of theseveral tubes are rotated at high angular velocities; for example, 100,and 1 kiloeycle per second. Since the pulse duration is 0f the order ofa microsecond or less, and the pulse repetition frequency is relativelylow, it follows that the beam rotating at 100 kilocycles per second willmake many revolutions for a single radial deflection corresponding to anapplied pulse. Therefore, the resultant radial trace can bedistinguished from the circular trace only with diiculty.

In a similar manner the more numerous circular or timing traces in anyof the timing tubes tend to obscure the less frequent radial or signaltraces. One of the objects of the instant invention is to provideimproved timing means for indicating the reception of radio pulses.Another object is to provide an improved cathode ray pulse timing systemin which the cathode ray timing traces are .blanked out except duringthe interval including the signal trace. Another object is to provide animproved decade type of cathode ray pulse timer in which the cathode raytiming sweeps may be applied to the fluorescent screen during anydesired portion of each timing sweep and biased oi during undesiredportions of the sweep whereby the signal traces may be readilydiscerned.

The invention will be described by referring to the accompanyingdrawings, in which Fig. 1 is a schematic diagram of one embodiment ofthe invention; Fig. 2 is a diagram of the blanking circuits used in theinvention; and Fig. 3 is a circuit diagram of. a delay network anddiscrimina.. tor circuit. Similar reference characters are applied tosimilar elements in the several figures.

Referring to Fig. 1, a radio pulse receiver I is connected through adiiierentiator 3 to the radial deflecting electrodes 5, 1 and `Ii of thecath-V ode ray tubes II, I3 and I5, respectively. The voltages forrotating the cathode ray beams areobtained as follows: A masteroscillator I'I, which is frequency controlled as hereinafter described,

is connected through an amplier I|9 and variable resistor to a deectingcircuit. The deecting circuit includes a conventional phase splitter 23,which proves a two-phase output. The twophase output currents areapplied to the deflect,- ing elements 25 of the rst cathode ray tube II.

'I'he master oscillator amplifier I9 is also connected to a 10 to 1counter circuit 21 which re duces the initial frequency by a factor of10, if the timing devices are to belof the decade type. The output ofthe counter circuit 21 is applied through a variable resistor 2'9 and adeecting circuit 3l, which includes a phase splitter, to the deflecting`elements 33 of the second cathode ray tube I3. The output of the countercircuit 21 is applied to a second 10 to 1 counter circuit 35. The outputof the second counter circuit is applied through a variable resistor 31and a delecting circuit 39, which includes a phase splitter, to thedeflecting elements 4I of the third cathode ray tube I5. l

Although not claimed as part of the instant invention, it is necessaryto describe the nature of the received pulses because components thereofare combined withlocal currents, derived from the master oscillator andthe successive counters terminating in counter 45, which are actuated bythe master oscillatorII, to control the master oscillator frequency andto synchronize n the master oscillator with the incoming pulses from oneof the transmitters. The transmitters are each arranged to radiate pairsof pulses. AFor example, the rst transmitter radiates two pulses with a.lve microsecond spacing; the second transmitter radiates two pulses Witha ten microseconds spacing; and the third transmitter radiates twopulses .with a fteen microseconds spacing. It should be understood that.the pairs -of pulses are radiated continuously from each transmitter ata rate of 331/3 pairs per second.v

These pulses are represented as pairs A, B and C at the receiver.

These pairs of pulses are fed from the receiver I through a delaynetwork 41 to a discriminator 49 which is responsive only to'pulsesapplied coincidentally. The delay network is tapped at three' points,5I, 53 and 55, so that any o-ne of three time constants may be selected.vThe rst time constant is chosen to bring together at the discriminator49 the pulses forming pair A; the second time constant brings togetherthe pulses of pair B; and the third time constant brings tgether thepulses of pair C. The discriminator 49 may be operated by any pair ofcoincidentally applied pulses, which are selected by the delay networkswitch 51. The output from the discriminator consists of single pulses59 which occur at the 331/3 per second repetition rate of the pairs.

A balanced modulator or differential bias circuit SI is connected to anautomatic frequency control circuit which is a part of the local masteroscillator I1. Pulses 59 from the discriminator 49 and currents from thecounter 45 are applied. to the inputs of the differential bias circuit.If the phase or frequency does not shift, the output of the dierentialcircuit will be Zero. If the phase of the local 331/3 cycles per secondcurrent changes with respect to the pulses, the differential circuitoutput will be of a polarity and of an amplitude suitable to increase ordecrease, as may be required, the master oscillator frequency. Thus thefrequency of the master oscillator is locked in to the incoming pulsefrequency. The range of lock-in may be indicated on a meter 63 connectedto the AFC and master oscillator circuit I1.

In the arrangement thus described the cathode ray beams of the threecathode ray tubes Ii, i3 and I5 are rotated by the currents derived fromthe master oscillator. The last tube i5, because of its low timing rateof .5 kilocycle per second. will indicate only large diiferencee in thetimes of arrival of the pairs of pulses A, B and C. The second tube I3,because of its intermediate timing rate of 5 kilocycles per second, willindicate intermediate time differences. The Vernier tube Ii. because ofits relatively high timing rate, will indicate slight or Vernierdifferences in the pulse arrival times.

As pointed out above, the low pulse frequency and the relatively hightiming frequency make it diicult to observe the radial traces producedby the pulses. This difficulty is overcome by applying the localcurrents of the pulse repetition irequency of 331/3 cycles per second toa multivibrator blanking circuit 65. The multivibrator circuit, whichwill be described hereinafter, incudes switches 51, 69 and 1I forconnecting adjustable resistors 13, or a short circuit connection Itacross elements of the circuit to vary its time or delay characteristic.Another resistor i1 is used to vary the width of the bianking pulse. Theoutput currents of the multivibrator are applied through leads 8I and 33to the grids of the several cathode ray tubes to blank out the beamexcept during a brief interval including the received pulses. While itis customary to describe the pulses as blanking pulses, it should beunderstood the blanking is effected by a combination of a steady gridbiasing potential plus an additional potential which, when applied tothe grid, allows the cathode rays to reach the fluorescent screen. Asused herein, the term blanking applies to the effective combination ofcathode ray biasing forces.

Referring to Fig. 2, the output of the counter 45 of Fig. l is appliedthrough a capacitor S5 to a pair of thermionic tubes 81, 89 which areconnected as a multivibrator. These tubes serve as delay tubes. Themanner of using a multivibrator as a delay tube is to make the outputrectangular wave of any desired length. By using the back or trailingedge of the rectangular wave to initiate or start a secondmultivibrator, the time delay may be adjusted by adjusting the length ofthe rst rectangular wave. The means for selecting and adjusting thedelay includes the resistors 13, 15 and the conductor 14 and the signalselector switches 61, 69 and 1 I. The currents from the counter 45 arealso applied through a capacitor 9! and resistor 93 to a second pair oftubes 95, 91 which are also connected as a multivibrator. The secondmultivibrator is used to produce a wide pulse. The output of the secondmultivibrator is applied through lead 99 and capacitor Il to a pair ofmixer tubes |93, |95 which may also serve as amplifiers.

Narrow pulses are obtained by applying the output from the delay tubes81, 89 to a third multivibrator which includes a pair of thermionictubes I1, |99 andthe adjustable resistor 11. The resistor 11 controlsthe width of the blanking pulses. The narrow pulses are app-lied througha lead I I3 and a capacitor I I5 to one of the mixer ampliiier tubesIGS. The wide and narrow pulses are combined in the mixer amplifier andare applied through the lead 8| to the grid of the cathode ray tube I5,whose beam is rotated most slowly. The narrow pulses of adjustable widthare applied by means of the lead G3 to the grids of the cathode raytubes I! and I3, whose beams rotate more rapidly than the beam blankedby wide and narrow pulses.

In practice, three pairs of spaced pulses are received. A pair of signalpulses A is applied to deiiect radially the beams of the cathode raytubes as the beams pass the Zero or other reference marks of the tubescales I2I. Since this requires no delay, the switch 69 is closed toblank the beams for all but the region nea-r Zero. The width of thenarrow blanking pulses is controlled by adjusting the width controlresistor 11. Inasinuch as the blanking pulses are synchronized with thelow frequency current derived from the master oscillator I1, it followsthat the blanking pulses will be synchronized with the incoming pulsesbecause the incoming pulses also control the master oscillator. Thus theblanking, local master oscillator, and received pulses are locked insynchronism.

When the pulse signals B from the second station are to be indicated,the switch G1 is opened; the switch 61 is closed; and the resistors 13are adjusted until the required amount of delay is obtained. In asimilar manner, when the pulse signals C from the third station are tobe received, the switches 61 and 69 are opened; the switch 1I is closed;and the resistors 15 are adjusted until the proper delay is obtained.The described blanking pulse delay should not be confused with the delaywhich is obtained in the delay network 41 to make the pulses of a paircoincide. The blanking pulse delay is used to apply the cathode raybeams to the fluorescent screens of the cathode ray tubes during theinstant when a particular pair of pulses is received and to bias off thebeam during all other periods. In the instant arrangement, the operatorselects the signals by closing any one of the signal selector switches61, 59 and 1I, and adjusts manually the delay which corresponds to thedifferences in the time required for the pulses to travel from theirrespective transmitters to the receiver. A circuit for automaticoperation is described and claimed in application Serial No. 420,919,filed November 29, 19'41, by John P. Smith, for Cathode ray pulseindicator.

As for the elements of the' system, the receiver I may be asuperheterodyne, tuned-radio frequency amplifier or any deviceresponsive to the pulse transmitters. The-diirerentiator 3 may be of thetype disclosed vin U. S. Patent No.

2,132,655. The delay network 41 may be a con,

Venticnal iilter with taps. at the desired intervals. The delay network4'I and the discriminator 49 may be of the design shown in Fig. 3. Asuitable form oi' diierential bias circuit GI isa balanced modulator ora circuit of the type clis-` closed in U. S. Patent 2,250,284, whichissued to K. R. Wendt on July 22,1941. The frequency dividers orcounters 27, 35, 43 vand 45 maybe of the type described in U. S. Patent2,258,943, which issued to A. V. Bedford on October 14, 1941. The masteroscillator, automatic frequency control, defiecting circuits, andcathode ray tube circuits, which are well known to those skilled intheart, do not require anyrdetailed disclosure.

In the operation of the described system, the pairs of pulses, which aretransmitted in predetermined time relation from a plurality oftransmitters at known locations, are received. The rst pair of pulses toarrive is preferably used to synchronize the local oscillator and toindica-te the reference or zero time of reception. The zero may bechecked by operating the signal selector switch 69. On cathode ray tubeI5 pulses are seen at all times at half brilliancy due to theapplication of both wide and narrow selector pulses. By properly timingthe narrow selector pulse, any particular pair of pulses may be broughtto full brilliancy on tube I5 to thus aid in selecting the correspondingpair on the two vernier tubes II and I3. On the Vernier of tubes Il andI3 the beam is blanked for all angular rotations of the beam except atthe times including the arrival of the pair of pulses A. Thereafter, theinterval of time between the arrival of the A and B pairs of pulses andthe interval between the arrival of the A and C pairs of pulses may beindicated by operating the switches 61 and 1I provided the associatedresistors have been adjusted to provide the desired blanking delay. Itshould be understood that, While both pulses of the pairs are shown onthe screen, the pulses of a pair could be made coincidental by selectingthe deecting pulses after the pairs of signal pulses pass through thediscriminator circuit.

We claim as our invention:

1. A radio pulse position indicating device including means forreceiving pulses of radio energy radiated in predetermined relation froma plurality of known locations, a source of local oscillations, a timingindicator, means connecting said source and said indicator for applyingsaid oscillations to drive said indicator at a substantially constantrate, means for generating blanking pulses, means connecting saidblanking pulse means to said indicator for applying said blanking pulsesto said timing indicator to eliminate all but a predetermined portion ofsaid timing indications, and means connecting said receiving means tosaid indicator for applying said received pulses to said indicator toindicate the differences in times of said pulse reception thereby toindicate the position of said receiver with respect to said knownlocations.

2. A radio pulse position indicating device including means forreceiving pulses of radio energy radiated in predetermined relation froma plurality of known locations, a source of local oscillations, a timingindicator, means connecting said source to said indicator for applyingsaid esciuauons to drive said indicator at a; substan-V tially constantYrate, means connecting said receiver and local source for synchronizingsaid local oscillations and said pulses, meansfor generating blankingpulses, means connecting said blanking pulse vmeans to said indicatorfor applying said blanking Vpulses to said timingl indicat'orftoeliminate all but a predetermined porn tion of saidtiming indications,and means connecting saidreceiving means to said indicator for applyingsaid received pulses to saidindicator to indicate the diierences intimes of said pulsey reception thereby to indicate the position of saidreceiverk with respect to said known locations.

= 3. A radio pulse position indicating .device in-v cluding means forreceiving pulses of radio energy radiated in, predetermined relationfrom a plurality of known locations, a source of local oscillations, atiming indicator, means connecting said source to said indicator forapplying said oscillations to drive said indicator at a substantiallyconstant rate, means for generating blanking pulses, means effectivelycoupling said source of local oscillations and said pulse generatingmeans Y- for synchronizing said blanking pulses with said localoscillations, means connecting said blank-v ing pulse means to saidindicator for applying said blanking pulses to said timing indicator toeliminate all but ar predetermined portion of said timing indications,and means connecting said receiving means to said indicator forapplyingsaid received pulses to said indicator to indicate thedifferences in times of said pulse reception thereby to indicate theposition of said receiver with respect to said known locations.

4. A radio pulse position indicating device including means forreceiving pulses of radio energy radiated in predetermined relation froma plurality of known locations, a source of local oscillations, a timingindicator, means connecting said source to said indicator for applyingsaid oscillations to drive said indicator at a substantially constantrate, means connecting said receiver and local source for synchronizingsaid local osy cillations and said pulses, kmeans for generatingblanking pulses, means effectively coupling said source of localoscillations and said pulse generating means for synchronizing saidblanking pulses with said local oscillations, means con- -necting saidblanking pulse means to said indicator for applying said blanking pulsesto said timing indicator to eliminate all but a predetermined portion ofsaid timing indications, and means connecting said receiving means tosaid indicator for applying said received pulses to said indicator toindicate the diierences in times of said pulse reception thereby toindicate the position of said receiver with respect to said knownlocations. Y

5. A device according to claim l including means for adjusting the widthof said blanking pulses.

6. A device according to claim 1 including means for delaying theapplication of said blanking pulses so that said timing indications arediscernible at the times oi:` reception of said pulses.

7. A radio pulse position indicating device including a pulse receiver,a cathode ray timing device including a uorescent screen, a source ofoscillations, means connecting said source to said Vtiming device forapplying said oscillations to drive said cathode ray as a timingindicator, means for blanking said ray from said screen, meansconnecting said receiver and said device 7 for deilecting said ray uponreception of pulses, and means for applying a biasing force to said raythereby to apply said ray to said screen during the deection of saidray.

8. A radio pulse position indicating device including a pulse receiver,a cathode ray tube in alud-ing a fluorescent screen and deectingelements, a source of oscillations, means connecting said source to saidtube for applying said oscillations to said deflecting elements todeilect said ray in synchronism with said oscillations, Ameans connectedto said tube for normally .biasing said' ray oilv said screen, meansconnected to said tube. and said receiver tofurtlier deflect said ray,biasing means connected to Said tube for applying said ray to saidscreen during the interval including said further deflection, and meansfor synchronizing said ray bias applying means with said localoscillations.

9. A radio pulse position indicating device including a pulse receiver,a cathode ray tube including a iluorescent screen and deflectingelements, a source of oscillations, means connecting said source to saidtube for applying said oscillations to said deecting elements to rotatesaid ray in synchronism with said oscillations, means connected to saidtube for normally biasing said rotating ray o said screen, meansconnected to said tube and said receiver to radially deflect saidrotated ray, biasing means connected to said tube ior applying said rayto saidv screen during the interval ncludingthe radialdeflection of saidray, and meansy for synchronizing said ray bias applying' means withsaid local oscillations.

l0. A device of the character of claim 9 including means for adjustingthe length of the interval during which said ray is applied to saidscreen.

1l. A radio Vpulse position indicating device including a pulsezreoeiver, a cathode ray tube including a fluorescent screen anddeecting elements, a source of oscillations, means forv applying saidoscillations to said deflecting elements to deect said rayV insynchronism With said oscillations, means connected to said receiver andto said tube for further deflecting said ray to indicate reception ofsaid pulses, and cathode ray blanking means connected to said tube andsaid source of oscillations 'including delay tubes connected together asmultivibrators and controlled by said oscillations Vwhereby said ray maybe biasedonto said screen during said further deilection.

l2. A device according to claim 1l including a second pair of tubesconnected together as a multivibrator and connected to said delay tubesfor controlling the width of said blanking pulses.V

RALPH S. HOLMES; JOHN P. SMITH.

